Multi-photon lithography

Abstract

A system and method for patterned exposure of a photoactive medium is described wherein a pulsed optical beam with a high peak-power is stretched in the time domain to reduce the peak power while maintaining the average power. The stretched pulse illuminated a pattern, such as a transparent or reflective photolithography mask. The pattern is then imaged onto the photoactive medium after recompressing the beam. This arrangement prevents damage to the mask by the high peak power of the pulsed optical beam.

1 . A microlithography system comprising 
 a light source producing a pulsed optical beam having a wavelength, a pulse duration and a peak power;    a pulse stretcher that receives the pulsed optical beam and increases the pulse duration of the pulsed optical beam while reducing the peak power;    a mask having a pattern defined thereon and illuminated by said stretched beam;    an optical element that images said illuminated pattern on a photoactive material; and    a pulse compressor disposed between the mask and the photoactive material, said pulse compressor decreasing the pulse duration and increasing the peak power of the stretched beam.    
   
   
       2 . The system of  claim 1 , wherein the photoactive material is a photon-activatable photoacid generator.  
   
   
       3 . The system of  claim 1 , wherein the photoactive material is a two-photon activatable photoacid generator.  
   
   
       4 . The system of  claim 1 , wherein the photoactive material is a multi-photon activatable photoacid generator.  
   
   
       5 . The system of  claim 1 , wherein the pulse stretcher comprises a grating pair.  
   
   
       6 . The system of  claim 1 , wherein the pulse stretcher comprises an optical fiber.  
   
   
       7 . The system of  claim 1 , wherein the pulse compressor comprises a grating pair.  
   
   
       8 . The system of  claim 1 , wherein the imaging optics comprises a reduction optics that reduces the feature size of the patterned mask.  
   
   
       9 . The system of  claim 1 , wherein the light source is a laser.  
   
   
       10 . The system of  claim 1 , wherein a wavelength of said stretched beam is frequency-converted from said wavelength to another wavelength that is shorter than said wavelength.  
   
   
       11 . The system of  claim 10 , wherein said other wavelength is produced by second, third or fourth harmonic generation.  
   
   
       12 . The system of  claim 1 , wherein the mask is a programmable mask.  
   
   
       13 . The system of  claim 12 , wherein the mask comprises a plurality of movable mirrors.  
   
   
       14 . The system of  claim 12 , and further comprising a liquid crystal modulator disposed in said stretched beam before the mask, said liquid crystal modulator modulating a phase, an amplitude or a polarization of said illuminating stretched beam, or a combination thereof.  
   
   
       15 . The system of  claim 1 , and further comprising an index matching fluid disposed between the optical element and the photoactive material.  
   
   
       16 . The system in  claim 5 , wherein said grating pair operates in a low diffraction order.  
   
   
       17 . The system in  claim 7 , wherein said grating pair operates in a low diffraction order.  
   
   
       18 . Method for patterned exposure of a photoactive medium, comprising: 
 producing a pulsed optical beam with a high peak-power;    stretching a pulse duration of the pulsed optical beam to reduce the high peak-power;    illuminating a pattern with the stretched pulse;    recompressing the stretched illuminated pattern; and    imaging the recompressed illuminated pattern onto the photoactive medium.    
   
   
       19 . The method of  claim 18 , wherein the recompressed illuminated pattern activates a photoactive process in the photoactive medium through multi-photon absorption.  
   
   
       20 . The method of  claim 19 , wherein the photoactive process produces a pattern in the photoactive medium having a feature size that is smaller than a diffraction-limited image of a corresponding feature size of the pattern.  
   
   
       21 . The method of  claim 20 , wherein the pattern in the photoactive medium is produced by repeatedly imaging the recompressed illuminated pattern onto the photoactive medium with a relative offset between repeated imaging steps, wherein a resulting separation between pattern features produced from different imaging steps is smaller than a diffraction-limited image of the pattern features.